This invention relates to magnetic printing heads, and in particular to a method of manufacturing high resolution transverse magnetic printing heads using electrodeposition.
Magnetic printing is a rapid and quiet system for producing images of both alpha-numeric and pictorial data. Magnetic printing basically involves the transfer of a dry magnetic ink from a ferromagnetic recording medium to a permanent paper medium. The magnetic ink is selectively attractive to portions of the recording medium by magnetizing portions of the magnetic recording medium through the use of a recording head which typically possesses a comb-like magnetically permeable structure. The teeth of the comb-like structure define gap regions between the teeth to facilitate the concentration of magnetic flux at the tips of the teeth. In a transverse printing head, these teeth tips are positioned in close proximity to the magnetic recording medium which is conventionally moved past the recording head so that the direction of motion of the recording medium is perpendicular to the direction of the magnetic flux lines between the tips of the teeth of the comb-like structure. Typically, a plurality of current carrying conductors pass through each of the gaps in the comb-like structure formed by its teeth and the current in these conductors controls the level of magnetic flux at the tips of the teeth of the comb. When sufficient current is passed through these conductors, the increased flux is sufficient to magnetize a selected portion of the recording medium which thereafter attracts magnetic ink to itself as the medium passes a magnetic brush assembly containing the magnetic ink. In this manner, the latent magnetic image impressed on the recording medium by the recording head is made visible. The recording medium with its magnetic ink images is then typically passed between heated rollers between which also passes a paper medium which receives the magnetic ink from the recording medium. The pattern on the magnetic recording medium is subsequently magnetically erased prior to the recording of new information thereon. A detailed description of magnetic printing and magnetic printing heads is found in U.S. Pat. No. 4,097,871, issued June 27, 1978 to Berkowitz et al. and assigned to the same assignee as the present invention, said patent being incorporated herein by reference.
The quality of an image that results is directly related to the resolution which is, in turn, directly related to the spacing between adjacent teeth of the magnetic comb-like structure. At a resolution of approximately 120 gaps or dots per inch, the spacing between adjacent comb teeth and adjacent conductive wires passing between the teeth is only approximately 5 mils. This is extremely tight spacing and it is often difficult to insert the comb into the substrate without bending wires or breaking teeth on the comb because of the delicate sizes involved. Moreover, if even higher resolutions, such as 200 dots per inch are desired, it does not appear to be possible to employ such a separate comb-like structure.